When short in length, a sump may be called a duck, however this can also refer to a section or passage with some (minimal) airspace above the water.
This is known as "free diving" and can only be attempted if the sump is known to be short and not technically difficult (e.g. constricted or requiring navigation).
Upstream sumps have been successfully emptied using hoses to siphon water out of them, such as at the Sinkhole Dersios during exploration in 2005.
During a rescue from beyond a downstream sump at Sarkhos Cave in 2002, water was pumped upstream into a dam constructed a few metres above the flooded passage.
Some manuals also mention the use of explosives or other forms of force to empty sumps, but the ecological damage done to the fragile cave environment usually rules out the use of such methods.